The prevention of adolescent drug and alcohol abuse requires an adequate understanding of not only the physiological bases of such behavior but of the psychological predispositioning factors as well. One variable that has been neglected in drug abuse research is the development of moral reasoning capacities in adolescence. Suggestion of cost/benefit decisions in drug abuse, studies of value differences between abusers and non-abusers, suggestions of moral components in rehabilitation, and evidence of a relationship between moral reasoning and illegal and antisocial behaviors all suggest that moral reasoning may play a significant role in the etiology of adolescent drug abuse. Nonetheless, the relationship is probably mediated by other variables. The most likely mediator is whether or not the adolescent perceives drug abuse behavior to be a moral issue. A recent model of social knowledge domains provides a means for exploring this mediating role. A second mediator and correlative variables is family process. Both the drug abuse and moral development literatures have revealed similar influences of the family on adolescent growth. Therefore a series of four studies are proposed to explore the relationship of moral reasoning to adolescent drug and alcohol abuse, including the mediating role of domain categorization and family confict resolution, drug history and parenting style. The first study will be a cross-sectional examination of moral reasoning, drug and alcohol abuse behavior, and domain categorization of drug abuse in 600 13-19 year old urban adolescents. Subjects will be individually interviewed to assess moral reasoning and domain categorization and will fill out anonymous drug use reports. In a second study of 1200 primarily minority 14-18 year old urban adolescents, the relationship of domains to drug abuse will be more intensively examined. Subjects will complete a detailed domain assessment and an anonymous drug use report. 120 subjects will also be intensively interviewed about domain categorization of drug abuse behaviors. The third study will be a longitudinal one-year exploration of the drug abuse and parental moral reasoning to adolescent drug abuse. All variables will be assessed at Time 1, and all but the family interaction will be repeated at Time 2. Fourth, psychiatric disorders will be separated from drug abuse in the relationship of moral reasoning to adolescent drug abuse.